Lifan 152F 2.5 hp engine won’t run? I may know why!

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Old 09-12-18, 01:09 PM
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Lifan 152F 2.5 hp engine won’t run? I may know why!

I’ve battled with this “won’t re-start once hot” problem for a couple of years. Now I know why!
 
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Old 09-12-18, 04:39 PM
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What is your discovery or question?
 
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Old 09-17-18, 08:11 AM
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As with most small engine non-start issues, yours may be the usual carburetor or spark problems, but my experience went much deeper than that.

Twice now, after using my pressure washer for an hour or so, I shut it down to refuel. When I attempted to re-start it following that, it wouldn’t hear of it. After diagnosing all the normal problems, it was still a no-go. I had spark, fuel in the bowl, and a clear air filter. With nothing to lose, I tore the Lifan 2.5 hp engine down, and found that the intake valve was seized in a partially open position. Applying copious amounts of WD-40 did nothing to free it up. When I had exhausted all the gingerly methods of removing the valve, I moved on to more aggressive tactics. I finally wrestled it out mm by mm by using channel lock pliers. I lubed everything, put it back together and it ran fine for a while. That was my first experience. When it happened again the next time I used it, I knew what to look for and immediately tore it down. Sure enough, the intake valve had seized again. Expecting the same result as the first time, I simply went to my drill index, selected a bit that was slightly larger diameter than the valve stem, and drilled out the valve bore. Once I reassembled the engine, it ran like a champ, and continues to at this time. Bottom line is: the intake valve guide bore is not large enough from the factory to allow sufficient clearance for the valve stem once everything expands from the heat of operation. This has been my experience. Hope it helps someone else, too.
 
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Old 09-17-18, 10:48 AM
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Generally this is caused by running stale gas. Something in stale gas leaves a hard thin film on the valve stem and guide and causes the valves to stick. Pressure washers, tillers, and generators are bad about this since they often sit unused for a long time and are more likely to be running on stale fuel.
 
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